MEMS (Micro Electro Mechanical Systems) is developed along with the development of integrated circuit manufacturing techniques, and integrated circuit manufacturing techniques and micro fabrication techniques are the basic manufacturing technologies of MEMS. Different from the integrated circuit which only includes connection between planar transistors and metal, MEMS includes numerous complex three dimensional micro structures and movable structures. These three dimensional micro structures and movable structures generally include a film support beam. For stress matching and electrical connection, the film support beams are usually composed of multi-layer films, and some of the films need to be patterned separately. For example, a support beam of an infrared sensor is composed of several layers of dielectric films/metal films, the metal films are used to be electrically connected to sensitive films and substrate processing circuits, thus it need to be patterned separately. Generally, only the metal layer on the support beam and a contacting hole are preserved. The most common technique of manufacturing the film support beam is to use one step of photoetching and etching to manufacture the film pattern on the support beam and the other area needed to be patterned separately, such as the metal layer in the support beam of an infrared sensor, and then a final support beam pattern is manufactured by one step of photoetching and etching, at last, the support beam is manufactured via releasing techniques. In view of the alignment error of photoetching, the width of the support beam manufactured by such technique has to be greater than the width of the metal layer pattern, in other words, according to such technique, the smallest size of the manufactured support beam equals to the minimum line width plus twice of the optimal registration accuracy. For example, if a process capability of a certain semiconductor production line shows that the minimum line width is 0.5 μm and the optimal registration accuracy is +/−0.35 μm, the smallest size of the support beam manufactured by such method is 1.2 μm, and such method has a relatively high requirement of the registration accuracy of photoetching, which increase a manufacturing difficulty.